Treatment of cyclic terpenes



United States Patent Oil-ice 3,028,418 Patented Apr. 3, 1962 TREATMENT FCYCLIC TERPENES Robert L. Webb, Jacksonville, Fla, assignor toThe'Glidden Company, Cleveland, ()hio, a corporation of Ohio N Drawing.Filed Sept. 7, 1955, Ser. No. 533,020 14 Claims. (Cl. 260-489) Thepresent invention relates to the treatment of cyclic terpenes having asingle cyclic double bond, and particularly relates to a treatment ofsuch terpenes of the pmenthane and pinane series in which the cyclicdouble bond involves the carbon atom carrying the methyl group, wherebythere are produced intermediates useful in the preparation of mentholand other p-menthane derivatives possessing an oxygenated substituent atthe 3-position.

The compounds contemplated as the starting materials for use in thepresent invention are such compounds as a-pinene, limonene,carvomenthene, a-terpineol, ethers of a-terpineol, such as the methylether, and the like. OL- Pinene and dl-limonene, commonly known asdipentene, are available in large quantities from turpentine. Alsosubstantial quantities ofdipentene and a-terpineol are obtained in thecommercial production of pine-oil from turpentine. Carvcmenthene isreadily produced by the partial hydrogenation of lirnonene since theexocyclic double bond is preferentially hydrogenated. Limonene is alsonow available in substantial quantities from the citrus fruit industry.

The conversion of these readily available terpene compounds to the morevaluable menthols and related materials is highly desirable, and it isaccordingly an object of the present invention to provide a process fortreating such terpene compounds so as to convert them into derivativesuseful in the preparation of compounds of the p-menthane series havingan oxygenated substituent in.

the 3-position.

Another object of the invention is to produce intermediates useful forthe preparation of menthol and related compounds.

An additional object is to provide a process for converting certainreadily available terpenic materials into more valuable terpeniccompounds possessing valuable odor and taste qualities.

A further object is to provide a novel process for introducing anoxygenated substituent into certain unsaturated terpene compounds.

Other objects will be apparent to those skilled in the art from thefollowing description of the invention.

It has been found that the foregoing objects can be accomplished byfirst treating the unsaturated compounds of the pinane and p-rnenthaneseries possessing a carboncarbon double bond involving the carbon atomcarrying the methyl group, which double bond is the sole cyclic doublebond, to chlorination in the presence of an alcohol and preferably inthe presence of a base, whereby the elements of RO-Cl are added to thedouble bond. In the reaction the R-O- radical adds to the trialkylatedcarbon atoms, and Cl adds to the dialkylated carbon atom involved in thedouble bond. Specifically, the chloroalkoxylation of carvomentheneyields both the 0L- and j3-forms of 1-methoxy-2-chloro-p-menthane, whichare cis-trans forms, although assignment of exact structuralconfiguration is not offered. Limonene yields the correspondingS-menthene compound. Where two forms of the same compound are produced,we refer to the lower boiling as the alpha-form and to the higherboiling as the beta-form.

The chloroalkoxy compounds are readily dehydrochlorinated by heating inthe presence of alkali or other dehydro-chlorinating agent with theformation of an allylic ether, which, when derived from carvomenthene,is 1- 2 alkoxy-2-menthene, and when derived from a-pinene is2-alkoXy-3-pinene.

Treatment of the others of the tertiary allylic alcohols with formicacid or other carboxylic acid readily yields the correspondingcarboxylic acid ester of the isomeric ailylic secondary alcohol, whichin the case of the 1- aikoxy-Z-menthene and formic acid is piperitylformate, and in the case of 2-alkoXy-3-pinene and formic acid isverbenyl formate. In the case of the piperityl esters, hydrolysis andhydrogenation, in either order, yield menthol.

The verbenyl ester, after hydrolysis, can be thermally isomerized asdisclosed in the copending application Serial No. 348,825, filed April14, 1953, now Patent 2,972,632, to yield isopiperitenol, which onhydrogenation yields menthol.

Similar considerations apply in the case of the overall process asapplied to limonene, a-terpineol, etc. Thus, treatment of the tertiaryaliylic ether obtained from limonene with formic acid yieldsisopiperitenyl formate.

In the case or a-terpineol, the 8-OH group can be readily removed bydehydration at any stage of the processing, asthis dehydration is quitereadily accomplished. Conveniently it can be accomplished during thehydrogenation step by proper choice of conditions and catalyst, such,for example, as disclosed in Simonsen, The Terpenes, 2nd ed., vol. 1,page 262.

The reactions involved, using formic acid, are illustrated in thefollowing equations for (a) carvomenthene as the starting material and(b) a-pinene as the starting material:

( OR OR 012 ROH 01 Base carvomenthene l-alkoxy-zl-alkoxy-2-chloro-p-menthane p-menthenc l H O O O H 0 H 0-CH menthyl formats HiO/Hz 1 H OH O-CH menthol plperltyl formate piperltol Base -H C l a-pinene2-alkoxy-3- 2-a1koxy chloro-pinane 3-pinene l HO O O H H A H O I 2 e lIi OH OH OH -OCH menthol isopiperitenol verbenol verbenyl(3-hydroxy-1imonene formate Since racemization does not occur in any ofthe reac tions involved, one can, by the proper choice of opticallyactive starting material and the selection of the proper intermediate,produce a menthol having the desired configuration. For example,hydrogenation of the cis-form of piperitol produced from di-limoneneleads predominately to di-neomenthol, and hydrogenation of the transformof the piperitol derived from l-limonene leads predominately todi-isornenthol. Thus, it is seen that when the substituents at the 3-and 4-positions of the p-methane derivative are trans, the hydrogenationis such that the l-methyl group is directed predominately cis to theisopropyl group, and that when the substituents at 3- and 4- are cis,the position of the l-methyl group on hydrogenation is predominatelytrans to the isopropyl group.

The configuration at the 1-position now having been fixed, the neoor theisomenthol can be subjected to one of the known equilibration treatmentsto form an equilibrium mixture of the isomeric menthols of the mentholfamily in which l-menthol predominates and which is separable from themixture by fractional distillation. If the starting hydrocarbon isdi-limonene, then the cispiperitol will yield l-men-thol when processedas above, and the trans-piperitolwill yield d-menthol.

The following examples are illustrative:

EXAMPLE 1 15,000 grams of d-limonene, B.P. at 100 mm., 110 C., N 1.4710,D 0.840, 11 (10 cm.)=+97.6, was hydrogenated in the presence of 0.2% byweight of 5.0% Pd on carbon at 35-70 C. under a hydrogen pressure of50-100 p.s.i.g. When one mole of hydrogen had been added, thehydrogenation was stopped and the product was filtered to removecatalyst. A small portion of the hydrogenation product was fractionatedthrough an efficient column at 100 mm. pressure. Comparison of infra-redspectra of the fractions with the spectra of known compounds indicatedthat the hydrogenation product was 8284% d-carvomenthene, B.P. at 100mm., 110 C., N 1.4594, D 0.825, x (10 cm.)+80, 8-10% p-menthane, cymeneand 12% unchanged d-limonene.

EXAMPLE 2 1000 grams of the filtered hydrogenationproduct from Example1, 82-84% d-carvomenthene, 3000 grams of methanol and 630 grams of NaHCOwere stirred at 15-20 C. while 425 grams of chlorine was bubbled intothe mixture. An ice bath was required to hold the temperature below 20C.

The reaction product was then diluted with 5000 ml. of water. The oilwas separated and dried to yield 1270 grams of chlorination product. Aportion of the chlorination product was fractionated through aneflicient glass packed column at mm. pressure. Infrared spectroanalysisof the fractions indicated that the chlorination product was 10-12%hydrocarbons, B.P. at 10 mm., 52- 60" C.; 2022% o-chloro-l-p-menthene,B.P. at 10 mm., C. to 97 C.; 6-8% 6-methoxy-l-menthene, B.P. at 10 mm.,86 0., N 1.4533, D 0.8811, (10 cm.) 12.02; 24-26%u-l-methoxy-2-chloro-p-menthane, B.P. at 10 mm. 104 0., N 1.4680, D0.9976, a (10 cm.) +45.0; 24-26% 5-1-methoxy-2-chloro-p-menthane, B.P.at 10 mm., 113-118 C., N 1.4746, D 1.0078, (10 cm.) -2.3; 10-12% highboiling materials, mostly dichlorides.

Identification of Products Comparison of infrared spectra with thespectra of known compounds indicated that the hydrocarbon fraction was amixture of cymene and p-menthane containing a trace of l-p-menthene.

The chloride fraction boiling at 95-97 C. was hydrolyzed by stirring itwith lime and water at 95-100 C. for 12 hours. Comparison of theinfrared spectrum of the hydrolyzed oil with a known spectrum of1-p-menthene-6-ol, carvotanacetol, showed them to be the same. Thus, thechloride must have been 2-chloro-6-p-menthene.

Infrared spectroanalysis of the fraction boiling at 86 C. at 10 mm.pressure indicated that it was an unsaturated ether as shown by thepresence of the characteristic trisubstituted ethylenic band absorptionat 12.3,u and the presence of the characteristic ether absorption at 9.2When 2chloro-6-p-menthene is treated with 10% KOH in methanol,6-methoxy-l-menthene is produced. The comparison of infrared spectrashowed that the other fraction present in the chlorination product waso-methoxyl-menthene.

Infrared spectroanalysis of the fraction boiling at 104- 118 C. at 10mm. pressure indicated that the compounds contained both chloro andether groups as shown by the presence of characteristic chloro and ethergroup absorptions at 13.2,u to 13.8 and 9.2;, respectively.Dehydrochlorination of the chloro other using KOH and diethylene glycolat 200 C. gave an unsaturated ether containing a symmetricallydisubstituted ethylenic bond as shown by the presence of thecharacteristic symmetrically disubstituted ethylenic bond absorption at13.7].L in the infrared spectrum. In the absence of any unlikelyrearrangements, the double bond of the unsaturated ether must be betweencarbon atoms 2 and 3. Thus, the chloro group of the chloro ether musthave been on either carbon atom 2 or 3. The above data indicate that ifthe chloro ether is formed by adding CH OCl to the double bond ofl-p-menthene, the chloro group must be attached to carbon atom 2 and theCH O group must be attached to carbon atom 1 giving1-methoxy-2-chloro-p-menthane. No investigation was made to determinethe stereochemistry of the chloro ether other than the observation thattwo stereoisorners were present.

' EXAMPLE 3 1000 grams of the filtered hydrogenation product fromExample 1 and 3000 grams of methanol were stirred while 425 grams ofchlorine was bubbled into the mixture. The temperature was maintained at-15-20 C. by using an ice bath. The reaction product was then dilutedwith 5000 ml. of water. The oil layer was separated and dried to yield1257 grams of chlorination product. The chlorination product wasfractionated through an efficient glass packed column at 10 mm.pressure. Infrared spectroanalysis of the fractions indicated that thechlorination product was 10-12% hydrocarbons, 8-10%6-methoxyl-p-menthene, 30-32% 6-chloro-1-p-menthene, 18-20%a-1-methoxy-2-chloro-p-menthane, 18-20% fi-l-rnethoxy-2-chloro-p-menthane, and 15-20% high boiling chlorides.

7 Example 1, 3000 grams of methanol and 630 grams of NaHCO were stirredwhile 425 grams of chlorine was 6.3 added. The reaction was held at50-55 C. by using an ice bath. The reaction product was diluted withwater and dried as shown in Examples 2 and 3. 1310 grams of driedchlorination product was obtained. Fractionation followed by infraredspectroanalysis of the fractions indicated that the chlorination productwas 12-15% hydrocarbons, 24-26% methoxy-l-p-inenthene, 2-4% 6-chloro-l-p-menthene, 24-26% oc-1-methoxy-2-chloro-pmenthane, 24-26B-1-methoxy-2-chloro-p-menthane,

23-10% high boiling chlorides.

EXAMELE 5 1000 grams of d-limonene, (10 cm.) +976", 3000 grams ofmethanol and 617 grams of NaHCO were stirred at 15-20 C. while 528 gramsof chlorine was bubbled into the mixture. An ice bath was required tokeep the temperature below 20 C. The reaction product was diluted with5000 ml. of water. The oil layer was separated and dried to yield 1290grams of chlorination product. Fractionation followed by infraredspectroanalysis of the fractions indicated that the chlorination productwas 10-15% hydrocarbons, 20-25% 6-chloro-1,8-pmenthadiene, B.P., 10 mm.,95-97 C., 510% 6-methoxy- 1,8-p-rnenthadiene, 3.1 10 mm., 87-88 C.,50-52% 1- rnethoxy-Z-chloro-S-p-menthene, B.P., 10 mm., 120 C., and 510%high boiling chlorides.

Identification of Compounds Comparison of the infrared spectrum of thehydrocarbon fraction with the spectra of known compounds indicated thatthis fraction was a mixture of cymene and unchanged limoneue.

6-chloro-l,8-p-rnenthadiene was identified as such by hydrolyzing it tocarveol by stirring it with Ca(OI-I) and water at 100 C. for 12 hours.

When 6-methoxy-1,8-p-menthadiene and l-methoxy-Z- chloro-8-p-mentheneare catalytically hydrogenated in the presence of 0.5% by weight of Ptat 2530 C. and under a hydrogen pressure of 40-60 p.s.i.g.,G-methoxyl-p-menthene and 1-methoxy-2-chlor0-p-menthane are formed, asshown by comparison of the infrared spectra with the spectra of thecompounds identified in Example 2.

EXAMPLE 6 1000 grams of oc-pinene, 3000 grams of methanol and 617 gramsof NaHCO were stirred at 15-20 C. while 528 grams of chlorine wasbubbled into the mixture. The reaction product was diluted with 5000grams of water. The oil layer was separated and dried to yield 1275grams of chlorination product. Fractionation followed by infraredspectroanalysis indicated that the chlorination product was 10-15%hydrocarbon, 20-25% pinocarvyl chloride, B.P., 10 mm., 80-85 G, -10%unsaturated ethers, B.P., mm., 72-78 C., mixture of pinocarvylmethylether and myrtenyl methyl ether, 40-45% 2-methoKy-3-chloropinane, B.P.,10 mm., 100-110 C. and 10-15% high boiling chlorides.

Identification 0] Compounds Infrared spectroanalysis of the hydrocarbonfraction indicated that it was predominately a-pinene.

Infrared spectronanalysis of the fraction boiling at 80- 85 C. at 10 mm.indicated that it contained a disubstituted terminal methylene as wellas a chloro group, as shown by the presence of the characteristicdisubstituted terminal methylene and chloro absorptions in the spectrumat 11.3 and 113.2-13.8[L, respectively.

Infrared spectroanalysis, after hydrolysis of this chloride by stirringit with Ca(0H) and water at 100 C., showed a decrease in the terminalmethylene absorption. Comparison of the spectrum of the hydrolisate withthe spectra of known compounds showed that the hydrolisate was a mixtureof pinocarveol and myrtenol. The above data indicate that the fractionboiling at 80-85 ,C. at 10 mm. was pinocarvyl chloride containingpossibly a small amount of myrtenyl chloride.

Infrared spectroanalysis of the fraction boiling at 72- 78 at 10 mm.indicated that it was a mixture of unsaturated ethers containing adisubstituted terminal methylene group and a trisubstituted ethylenicbond, as shown by the presence of the characteristic disubstitutedterminal methylene group and the trisubstituted ethylenic bondabsorption in the spectrum at 113p and 123 11., respectively. Treatmentof a sample of pinocarvyl ch1oride (the fraction boiling at 8085 C. at10 mm.) with 10% KOH in methanol gave a material having an infraredspectrum identical with the unsaturated ethers obtained fromfractionation of the chlorination product. It is known that thetreatment of pinocarvyl chloride with methanolic KOH yields a mixture ofpinocarvyl methyl ether and myrtenyl methyl ether. From the above data,it is evident that the fraction boiling at 72-78 C. at 10 mm. is amixture of pinocarvyl methyl ether and myrtenyl methyl ether.

Infrared spectroanalysis of the fraction boiling at C. at 10 mm.pressure indicated that the compound contained both ether and chlorogroups, as shown by the presence of the characteristic ether and chlorogroup absorptions in the spectrum at 9.2 and 13.2-13.8p, respectively.Dehydrochlorination of a sample of the chloro other compound using KOHand diethylene glycol at -205 C. gave an unsaturated ether containing asymmetrically disubstitutcd ethylenic bond, as shown by the presence ofthe characteristic disubstituted ethylenic bond absorption in theinfrared spectrum at 13.7 In the absence of any unlikely rearrangementof the pinane skeleton, the double bond must be between carbon atoms 3and 4. Thus, if CH OCl was added to the double bond of a-pinene duringthe chlorination, the chloro group must be attached to carbon atomnumber 3 and the methoxyl group attached to carbon atom number 2. Fromthe above data, it is evident that the fraction boiling between 100-110C. at 10 mm. pressure is 2-methoxy-3- chloro-pinane and that thedehydrochlorination product is 2-methoxy-3rpinene. See also Example 21for conversion of the latter compound to verbenol.

EXAMPLE 7 500 grams of a-terpineol, 1500 grams of methanol, 340 grams ofNaHCO were stirred, while 230 grams of chlorine was bubbled into themixture at 15-20 C. The reaction product was washed with 2500 ml. of H 0and dried to yield 672 grams of chlorination product. The chlorinationproduct was fractionated through an efficient glass packed column at 1.0mm. pressure. Infrared spectroanalysis of the fractions indicated thatthe chlorination product was 5-10% hydrocarbons, 3-5% unchangedOlterpineol, 5-10% (S-methoxy-l-p-menthene-8-ol, B.P., 1.0 mm., 73-77C., 15-20% 6-chloro-1-p-menthene-8-ol, B.P., 1.0 mm., 80-87 C., 55-60%l-methoxy-Z-chlorop-menthane-S-ol and 5-10% unidentified high boilingcompounds.

Identification of Compounds Comparison of the spectrum of thehydrocarbon fraction with the spectra of known compounds showed that itwas a mixture of cyrnene and monocyclic terpenes (limonene, terpinolene,terpinenes).

The fraction boiling at 73-77 C. at 1.0 mm. was a hydroxy ether, asshown by the presence of the characteristic hydroxyl and etherabsorptions in its infrared spectrum at 3.0,u and 9.2;, respectively.Dehydration of the compound by heating it to 173 C. in the presence of atrace of iodine gave 6-methoxy-2,8-p-menthadiene (carvyl methyl ether),as shown by infrared spectroanalysis. The fraction boiling at 73-77 C.at 1.0 mm. pressure, therefore, was 6-rnethoxy-1-p-menthene-8-ol.

The fraction boiling at 8087 C. at 1.0 mm. was identified as a hydroxychloride, as shown by the presence of the characteristic hydroxyl andchloride absorptions in its infrared spectrum at 3.0,u and 9.2respectively. Treatment of the hydroxy chloride with a solution of 10%KOH in methanol gave 6-rnethoxy-l-p-menthene-8-ol, as shown by infraredspectroanalysis. It was identical with the product so identified abovethrough dehydration to carvyl methyl ether.

Infrared spectroanalysis of the residue indicated that it waspredominately a single compound. The compound contained a hydroxylgroup, a chloro group and an ether group, as shown by the presence ofthe characteristic hydroxyl, chloro and ether absorptions in thespectrurn at 3.0 13.2-13.8;i and 9.2;, respectively. The CH OCl adds tothe double bond of ct-IGIPiDBOl as it added to carvomenthene, a-pineneand limonene. The compound present in the residue isl-methoxy-Z-chlorop-menthane-S-ol, therefore.

EXAMPLE 8 500 grams of the filtered hydrogenation product from Example1, 2160 grams of ethanol and 315 grams of NaHCO were stirred at 15-20C., while 212 grams of chlorine was bubbled into the mixture. An icebath was required to hold the temperature below 20 C. The reactionproduct was then diluted with water. The oil layer was isolated anddried to yield 620 grams of chlorination product. Infraredspectroanalysis of the chlorination product indicated that it contained20-25% 1- ethoxy-2-chloro-p-menthane.

EXAMPLE 9 500 grams of the filtered hydrogenation product from Example 1(82-84% d-carvomenthene), 2800 grams isopropanol and 315 grams ofNaI-ICO were stirred at 15-20 C., while 212 grams of chlorine wasbubbled into the mixture. The reaction product was then washed withWater. The oil layer was isolated and dried under vacuum to yield 615grams of chlorination product. Infrared spectroanalysis of thechlorination product showed that it contained 5-10% of the tertiarychloro ether.

EXAMPLE 300 grams of a mixture of the a and ,8 forms of 1-methoxy-Z-chloro-p-menthane from Example 2, 150 grams of KOH and 150grams of diethylene glycol were stirred for 3 hours at 195-205 C. atatmospheric pressure. The reaction product was then distilled 01f to apot temperature of 230 C. 215 grams of distillate was obtained.Fractionation of the distillate, followed by infrared spectroanalysis ofthe fractions, indicated that it consisted of 12% hydrocarbons, BR, 10mm., 52- 58 C., 60-65% or-l-methoxy-Z-p-menthene, BR, 10 mm., 76.5 C., N1.4540, DE 0.8758, 10 cm., 2.45, 15-20% fi-l-rnethoxy-Z-p-menthene, RR,10 mm, 80 C., N 1.4553, D 0.8799, 10 cm., +15.3, and 35% unchangedl-methoxy-2-chloro-pmenthane.

Identification 0} Compounds Infrared spectroanalysis of the hydrocarbonfraction indicated that it was largely p-cymene containing small amountsof a-terpinene and phellandrenes.

Infrared speetroanalysis of the fractions boiling at 765 C. and 80 C. at10 mm. indicated that they were unsaturated ethers containing asymmetrically disubstituted ethylenic bond as shown by the presence ofthe characteristic ether and symmetrically disubstituted ethylenic bondabsorptions at 9.2a and 13.7/L, respectively. Thus, the double bond ofthe unsaturated ethers must be in the 2-3 position. Oxidation of theindividual unsaturated ethers with Na cr o and aqueous H 80 Beckmannmixture, gave d-piperitone, B.P. 102-103 C., 0: 10 cm., +41. From theabove data, it is evident that the ethers are stereoisomers ofl-methoxy-Z-p-menthene, each of which is capable of yieldingd-piperitone.

EXAMPLE 11 200 grams of a mixture of the a and ,8 forms of 1-methoxy-Z-chloro-p-menthane and grams of KOH were stirred for 8 hours at195-205 C. The reaction product was distilled from the reaction flask toa pot temperature of 230 C. grams of distillate was recovered. Infraredspectroanalysis of the distillate indicated that it was 15-20% eymene,50-55% l-methoxy- 2-p-menthene, mixture of or and [3 forms, and 25-30%unchanged 1-methoxy-2-chloro-p-menthane.

EXAMPLE 12 200 grams of 1-rnethoxy-2chloro-p-menthane, 100 grams ofdiethylene glycol and 100 grams of NaOH were stirred for 6 hours at -205C. The reaction product was then distilled from the reaction flask to apot temperature of 240 C. at atmospheric pressure. 153 grams ofdistillate was recovered. Infrared spectroanalysis of the distillateindicated that it contained 5-8% hydrocarbons, 50-45%1-methoxy-2-p-rnethene, mixture of a and 18 forms, 45-50% unchangedl-rnethoxy-Z-chlorop-menthane.

EXAMPLE 13 300 grams of the crude chlorination product from Example 2,75 grams of KOH and 75 grams of diethylene glycol were stirred for 4hours at 195-205 C. The reaction product was then distilled from thereaction vessel to a pot temperature of 230 C. and 246 grams ofdistillate was recovered. Fractionation of the distillate, followed byinfrared spectroanalysis of the fractions, indicated that it was 40-45%hydrocarbons comprising cymene, menthane, a-terpinene and phellandrenes,38- 42% 1-methoxy-2-p-rnenthene, 10-15% 6-methoxy1-pmenthene and 2-4%unchanged 1-methoxy-2-chloro-pmenthane.

EXAMPLE 14' 300 grams of a mixture of a and ,8 forms ofl-methoxy-2-ch1oro-8p menthene, 150 grams of diethylene glycol and 150gramsof KOH were stirred at 195-205 C. for 4 hours. The reaction productwas then distilled from the reaction vessel to a pot temperature of 230C. and 207 grams of distillate was recovered. Fractionation of thedistillate, followed by infrared spectroanalysis of the fractions,indicated that it was 15-20% hydrocarbons, 70-75%1-methoxy-2,S-p-rnenthadiene, B.P., 10 mm., 75- 82 C., 3-5%1-methoxy-2-chloro-8-p-menthene.

Identification of Compounds Infrared spectroanalysis of the hydrocarbonfraction indicated that it was very pure cymene.

Infrared spectroanalysis of the fraction boiling at 75- 82 C. at 10 mm.indicated that it was an ether containing a disubstituted terminalmethylene group and a symmetrically disubstituted ethylenic double bondas shown by the presence of the characteristic ether, disubstitutedterminal methylene and symmetrically disubstituted ethylenic bandabsorptions at 9.2 11.3,u and 13.7,u, respectively. The catalyticaddition of one mole of hydrogen to this fraction at 2025 C. in thepresence of 0.2% by weight of PtO under a hydrogen pressure of 40-60p.s.i.g. gave a mixture of the a and 5 forms of l-methoxy-2-menthene asdetermined by infrared spectroanalysis. From the above data it isevident that the fraction boiling at 75-82 C. at 10 mm. pressure is amixture of the two stereoisomeric forms of 1-rnethoxy-2,8-p-menthadiene.

EXAMPLE 15 300 grams of 2-methoxy-3-chloro-pinane, 150 grams ofdiethylene glycol and 150 grams of KOH were stirred at 195-205 C. for 4hours. The reaction product was then steam distilled to yield 220 gramsof distillate. Fractionation of the distillate, followed by infraredspectroanalysis of the fractions, indicated that the distillate was8-10% hydrocarbons, 60-65% 2-methoxy-3-pinene, BR, 10 mm., 65-68 C., and20-25% unchanged 2-methoxy- 3-chloro-pinane.

Identification of Compounds and 4. Oxidation of this fraction with Na CrO and.

aqueous H SO at 20-25 C. gave verbenone, B.P., 10 mm, 96-98 C., as shownby comparison of the infrared spectrum of the oxidation product with thespectrum of a known sample of verbenone. From the above data, it isevident that the fraction boiling at 65-68 C. at 10 mm. is2-methoxy-3-pinene.

EXAMPLE 1'6 200 grams of crude 1-methoxy-2-chloro-p-menthane-8- 01, asprepared in Example 7, 100 grams of diethylene glycol and 100 grams ofKOH were stirred at 195-205 C. for 4 hours. The reaction product'wasthen steam distilled to yield 121 grams of distillate. Fractionation ofthe distillate, followed by infrared spectroanalysis of the fractions,indicated that the distillate was 3-5 hydrocarbons, 35-40%1-methoxy-2-menthene-8-ol, B.P., 10 mm, 118-120" C., and 50-55% of acompound that is believed to be 1-methoxy-2,S-epoxy-p-rnenthane, B.P.,10 mm., 103-105 (3., N 1.4765.

Identification Compounds The fraction boiling at 118120 C. at 10 mm. wasan unsaturated hydroxy ether having a symmetrically disubstitutedethylenic bond as shown by the presence of the characteristic hydroxyl,ether and symmetrically disubstituted ethylenic bond absorptions in theinfrared spectrum at 3.011., 9.2a and 137 respectively.

Infrared spectroanalysis of the compound boiling at 103-105" C. at 10mm. pressure indicated that it was an epoxy-ether, as shown by thepresence of the characteristic epoxy and ether absorptions at about 9.7and 9.2 respectively. The compound is believed to be 1-methoxy-Z,8-epoxy-p-menthane.

EXAMPLE 17 300 grams of a mixture of the a and forms of 1-methoxy-Z-p-menthene, 300 grams of Na- Cr O and 1200 ml. of water werestirred at 20-25 C. while 2000 grams of 50% by weight aqueous H 80 wasadded slowly. An ice bath was required to hold the temperature below 25C. After all of the H SO solution had been added, the reaction mixturewas stirred one hour at 20-25 C. The oil layer was then separated. Theaqueous layer was extracted with ether and the ether extract wascombined with the oil layer. The ether was removed to yield 106 grams ofoxidation product. Fractionation of the oxidation product, followed byinfrared spectroanalysis of the fractions, indicated that the oxidationproduct was 25-30% hydrocarbons and 65-70% piperitone, B.P., mm.,102-103 C., and 7% residue. The structure of the piperitone was provedby comparing its infrared spectrum with the spectrum of a known sampleof piperitone.

EXAMPLE 18 300 grams of 90% formic acid and 45 grams of anhydrous sodiumacetate were mixed and precooled to 0-5 C; This mixture was added slowlyto 300 grams of 1- methoxy-2-p-menthene at 0-5 C. with stirring. Aftertwo hours the stirring was stopped and the oil layer separated. Infraredspectroanalysis of the oil layer indicated that part of thel-methoxy-Z-p-menthene had been converted to an ester. The ester wassaponified by stirring it with aqueous NaOH at -100" C. for 8 hours.

The saponified oil, 250 grams, was then fractionated through anefiicient column at 10 mm. pressure. Infrared spectroanalysis of thefractions indicated that the saponified oil contained 510% hydrocarbons(mixture of aterpinene and phellandrenes), 55-60% unchanged 1-Inethoxy-2--p-menthene, 15-18% cis-piperitol and 15-18% trans-piperitol.T he products were identified by comparing their infrared spectra withthe spectra of the known compounds.

EXAMPLE 19 690 grams of a precooled formic acid-sodium acetate mixture,prepared in the proportions used in Example 18, was slowly added to 600grams of dehydrochlorination product, prepared as shown in Example 13and having the same composition. The reaction mixture was stirred for 2hours at 0-5 C. The oil layer was thenseparated, saponified andfractionated as shown in Example 18. Infrared spectroanalysis of thefractions indicated that the saponified oil, 542 grams, was 45-50%hydrocarbons, 55-10% 1-methoxy-2-p-menthene, 10-12% 6-methoxy-1-p-menthene, and 25-30% piperitols composed of about equai parts of thecis and trans forms.

EXAMPLE 20 300 grams of 1-methoxy-2,S-p-menthadiene was agitated with anequal weight of a sodium acetate-formic acid mixture at 0-5 C. for twohours and treated as shown in the previous examples. The saponified oil,257 grams, was fractionated and the fractions were analyzed by infraredspectroanalysis. The saponified oil consisted of 5-10% hydrocarbon,50-60% unchanged 1-- methoxy-Z,S-p-menthadiene and 30-35%isopiperitenol. Thecatalytic addition of one mole of hydrogen to theisopiperitenol at a hydrogen pressure of 40-60 p.s.i.g. in the presenceof 0.5% by weight of Raney nickel catalyst at 20-30 C. gave a mixture ofcis and trans piperitols as determined by infrared spectroanalysis.

EXAMPLE 21 200 grams of 2-methoxy-3-pin-ene was treated with 230 gramsof the sodium acetate-formic acid mixture by the procedure shown inExamples 18 and 19. The saponified oil obtained, 158 grams, was 30%trans-verbenol and 60- 70% unchanged 2-methoxy-3-pinene as shown byinfrared spectroanalysis.

' EXAMPLE 22 A solution of 150 grams sodium acetate in 1000 grams of 85%formic acid was cooled to 0-5 C. and added to a mixture of the alpha andbeta forms of l-methoxy-Z-pmenthene precooled to about the sametemperature. The ether mixture had been prepared from d-limonene by theprocedures disclosed herein, and it was accordingly optically active.After the mixture was stirred for two hours, the layers were allowed toseparate and the upper oil phase subjected to a saponification. Thesaponified oil, 285 grams, was fractionated to yield 5-10% hydrocarbons,55-60% unchanged l-methoxy-Z-p-menthene, 15-18.% cis-piperitol and15-18% trans-piperitol. The individual piperitols were purified bypartial crystallization and centrifuging to yield piperitols having thefollowing properties:

grams of each of the purified piperitols was hydrogenated at 50-70 C. inthe presence of 1.0% by weight of Raney nickel cataiyst under a hydrogenpressure of 100-500 p.s.i.g. The hydrogenation product was filtered andfractionated. The fractions were analyzed by infrared spectroanalysis.The hydrogenation of the d-cispiperitol gave a hydrogenation productthat was 92-95% neomenthol, 5-7% other stereoisomers of menthol.Fractional distillation of the hydrogenation product gave high purityd-neomenthol, 1 +19.1.

The hydrogenation of l-trans-piperitol gave a hydro genation productthat was 95% isomenthol and 5% other stereoisomers of menthol asdetermined by infrared spectroanalysis. Fractional distillation of thehydrogenation product gave high purity l-isomenthol, 26.4.

EXAMPLE 23 200 grams of cis-piperitol, 01 (10 cm.) +225", was mixed atto C. with 460 grams of a mixture of 400 grams of 90% formic acid and 60grams of sodium acetate. The materials gave a clear solution whichbecame cloudy after 15 minutes. After one hour, an oil layer hadseparated. Saponificatio-n of the oil layer with an excess of a 25%solution of NaOH at 100 C. gave 189 grams of oils, oc cm.) +78.Fractionation of the saponified oil through an efficient column followedby infrared spectroanalysis of the fraction showed that the saponfiedoil yielded 35% hydrocarbons; 3-5% Z-p-menthene-l-ol, B.P., 10 mm.,85-90 C.; 45-50% cis-piperitol, (x (10 cm.) +220; and 40-45%transpiperitol, a (10 cm.) '51.

The fraction boiling at 85-90 C. at 10 mm. was an unsaturated tertiaryalcohol having a symmetrically disubstituted ethylenic bond as shown bythe presence of the characteristic tertiary alcohol and symmetricallydisubstituted ethylenic bond absorption in the infrared spectrum at 9.31 and 13.7,u, respectively. Treatment of the tertiary alcohol mixturewith a sodium acetateformic acid mixture followed by saponification gavea mixture of piperitols as determined by infrared spectroanalysis.

EXAMPLE 24 200 grams of trans-piperitol, 04 (10 cm.) 51, was treatedwith a mixture of 60 grams sodium acetate and 400 grams 90% formic acidat 9-5 C., and the ester which separated after standing one hour wassaponified as shown in the previous example. Infrared spectroanalysis ofthe saponified oil, (x (10 cm.) +75, was 3-5% hydrocarbon, 3-5%2-p-methene-1-ol, 45-55% cis-piperitol and 45-50% trans-piperitol.

EXAMPLE 25 500 grams of the filtered hydrogenation product from Example1, 82-84% d-carvomenthene, 1500 grams of methanol and 315 grams of NaHCOwere stirred at -20 C. while 21.3 grams of chlorine was bubbled into themixture. The methanol was then removed by distilling at atmosphericpressure to a pot temperature of 80 C. The methanol-free chlorinationproduct was then filtered to remove inorganic salts. The filtered oilwas then fractionated through an efficient column at 10 mm. pressure.Infrared spectroanalysis of the fractions indicated that thechlorination product was -25% hydrocarbons; 20-25%6-methoxy-l-p-menthene; 3-5% 6-chloro-1-p-menthene; 48-52%1-methoxy-2-chloro-prnenthane, a mixture of 0c and ,5 forms; and 35%higher boiling chlorides.

EXAMPLE 26 500 grams of 6-methoxy-1-p-menthene and 500 grams of 90%formic acid were heated at 50 C. for two hours. The reaction mixture wasthen diluted with water. The oil layer was saponified using an excess ofan aqueous NaOH solution at 100 C. The saponified oil, 433 grams, wasfractionated through an efficient column at 10 mm. pressure. Infraredspectroanalysis of the fractions indicated that the saporn'fied oil was35-40% hydrocarbons, 5-l0% unchanged 6-methoxy-1-p-mentheme and 50-55%1-p-menthene-6-ol, carvotanacetol, B.P., 10 mm., 102 C., N 1.4790.

12 EXAMPLE 27 300 grams of trans-pipertol, (x (10 cm.) 49, was addedslowly to a mixture of 600 grams of 90% formic acid and 90 grams ofanhydrous sodium acetate at 0-5 C. The reaction mixture was stirred at0.5 C. for one hour. The oil layer was then separated and washed with aNal-ICO solution to remove unreacted formic acid. The washed oil, 373grams, was then fractionated through an efficient column at 10 mm.pressure to yield 5-l0% hydrocarbons, -90% piperityl formate, mixture ofcis and trans, B.P., 10 mm., 96-100 C., N 1.4646, D 0.9545, 04 (10 cm.)+36", and 3-5% unchanged piperitols. Saponification of a portion ofpiperityl formate fraction gave a mixture of cisand trans-piperitols.

EXAMPLE 28 200 grams of 1-cis-piperitol, 01 (10 cm.) -255, is treatedwith 500 ml. glacial acetic acid at 10 C. The homogeneous solution isallowed to stand for 48 hours at 10 to 25 C., and then the excess aceticacid is removed by water wash. After neutralizing the oil layer bywashing it with sodium bicarbonate solution, the ester is fractionatedat 5 mm. pressure. After removal of a small amount of free alcohols,B.P. 70-85 (1., containing some Z-menthene-l-ol, the pure piperitylacetate, B.P. -95 C. at 5 mm. distills. The ester shows N 1.462, D0.950, oz --31 (10 cm. tube). On saponification it yields a mixture ofl-cis and d-trans piperitols.

The foregoing examples are illustrative and many variations therein arepossible. Other alkaline reagents can be used for the alkoxychlorination step, or such reagents can be omitted entirely, although Iprefer to employ a base. Any suitable base can be used for thedehydrochlorination step, but this is preferably a strong base, andorganic bases, such as pyridine, collidine, etc., can be used, as wellas the inorganic bases. Also other alcohols can be used, particularlythe lower alcohols, such as ethyl, propyl, etc. for the alkoxychlorination, but it will be found that the yield of the desired alkoxycompound will be appreciably less and I therefore prefer to employmethanol. Due to its cheapness, availability and suitability, methylalcohol will ordinarily be preferred.

The pyrolysis of the verhenol and the isopiperitenol described herein isdescribed and claimed in the copending application of Bain et al.,Serial No. 348,825, filed April 14, 1953, now Patent 2,972,632, and theuse of formic acid and other carboxylic acids for the conversion of thetertiary allyl alcohol ethers to the secondary allyl alcohol formates isdescribed and claimed in the copending application of Bain, Serial No.533,234, filed September 7, 1955, now Patent 2,935,526. Thus, while theinvention has been illustrated with formic acid and its use ispreferred, other carboxylic acids can be used.

It will also be appreciated that other terpenes possessing the samestructure as that common to a-pinene and carvomenthene can be employedfor the chloro alkoxylation treatment, such as 3-thujene and 3-carene.

In conducting the chloralkoxylation, the terpenic compound and the loweralcohol, such as methanol, are mixed and preferably agitated as chlorineis fed into the mixture. The proportions of the ingredients are notcritical, but we prefer to employ a several-mole excess of the alcoholand to employ about one mole of chlorine per mole of terpenic compound.While it is not necessary to employ a base to absorb the by-producthydrogen chloride formed, I prefer to employ a base in quantity somewhatin excess of that required in order that the excess alcohol can berecovered more or less acid-free and to improve the yield of chloralkoxycompound. The reaction proceeds exothermically, but smoothly. Thetemperature is not critical, but I find temperatures of 20 to 80convenient and easy to maintain by cooling. Further, quite lowtemperatures, say 10 C. and below, favor formation of undesirabledichlorides, where- 13 as temperatures above 80 C. tend to favorformation of allylic chloride at the expense of desired chloralkoxycompound.

The reaction is substantially complete as soon as all the chlorine hasbeen added, and the product can be worked up immediately.

In working up the product, I can add water and separate the organicchloride layer from the aqueous layer and then distill or otherwisetreat the organic chlorides. However, I find it convenient to simplydistill the relatively low boling excess alcohol away from the organicchlorides and recover it for reuse. If a base is employed during thechlora-lkoxylation, the product can be filtered to remove inorganicsalts prior or subsequent to the distillation of alcohol.

As shown in the examples, the chloralkoxylation is generally accompaniedby some allylicchlorination and some formation of dichlorides. Thus,some 6-chlorol-p-menthene, carvotanacetyl chloride, may be formed whencarvomenthene is chloralkoxylated, and some 1,2- dichloro-p-menthene maybe present in the reacted product. Further, the allylic chloride willtend to react more or less with the alcohol employed to form the ether.Thus, when carvomenthene is chlorornethoxylated, more or lesscarvotanacetyl methyl ether is produced through reaction ofcarvotanacetyl chloride with the methanol. If the chlormethoxylationtakes place in the presence of a base such as sodium bicarbonate and theexcess methanol is distilled off at the end of the reaction, littlecarvotanacetyl chloride will be found since most of it will be convertedto carvotanacetyl methyl ether. On the other hand, if thechloralkoxylation is conducted at low temperature and the methanol iswished out of the reaction product prior to heating the product, then aconsiderable amount of the carvotanacetyl chloride originally formedremains as such and less etheris formed.

carvotanacetyl methyl ether can be used as a high boiling solvent or canbe split to carvotanacetol and methanol .by treatment with formic acid,followed by saponification of the esters formed. carvotanacetyl chlorideis readily converted to ethers by heating it with an'alcohol, preferablyin presence of a base. Alternatively, the chloride can be hydrolyzed tothe alcohol easily by heating it with water and a base.

After its isolation the crude organic chloride-ether product can befractionally distilled to isolate its individual components, or it canbe employed directly for dehydrochlorination. Thus, the reaction productfrom chlorination of carvomenthene and methanol can be dis.- tilled torecover hydrocarbons, if any, carvotanacetyl methyl ether,carvotanacetyl chloride, if any, and the lower, alpha, and higher, beta,boiling forms of l-methoxy-2-chloro-p-menthane, and finally the highestboiling fraction rich in 1,2-dichloro-p-menthane. The chloromethoxycompound, either or both forms, then readily yields l-methoxy-Z-menthenein readily purifiable form when subjected to dehydrochlorination.

Alternatively, the crude chlormethoxylated product can bedehydrochlorinated and then fractionated to obtain the desiredl-methoxy-Z-menthene, alpha and beta forms.

In conducting the dehydrochlorination, the alkoxychloride containingproduct is heated with a base capable of at least partially neutralizingthe hydrogen chloride evolved through the thermal decomposition of thealkoxychloride. Various bases can be employed, of course, but a suitableand convenient base is potassium hydroxidediethylene glycol mixture.Presence of alcohols such as glycols tends to solubilize the alkali andmake it more readily available for reaction. The pure alkoxy chloridedecomposes only slowly below about 175 C., and at high temperatures, say250 C. or higher, the l-alkoxy-Z-menthene tends to decompose somewhat.The optimum temperature of dehydrochlorination is, therefore, within therange of 175 to 250 C., though temperatures outside this range areoperable. I find it convenient and satisfactory to simply heat thealkoxychloride, pure or impure, with a base and under atmosphericpressure until the product begins to boil and to distill the productslowly as the dehydrochlorination progresses.

Impurities such as hydrocarbons and carvotanacetyl methyl ether, as wellas the desired l-methoxy-Z-menthene, all boil below the boiling point ofl-methoxy-Z- chloro-p-menthene, and therefore the reaction anddistillation can be conducted with a column so as to distill off thechlorine-free products while condensing the chlorinated products andreturning them to the reactor containing the base. In this way it ispossible to recover a distillate containing a little chlorides or almostfree of chlorides and in 'very good yield. Very little unreactedchlorides remain in the reactor with the base.

Alternatively, the reaction can be completed without distillation ifdesired, and. either at atmospheric or superatmospheric pressure, and atthe end of the reaction the water-soluble glycol or inorganic chloridescan be removed by washing.

The substantially chloride-free unsaturated ethers can be fractionatedto secure the pure alpha and beta forms of Lmethoxy-Z-menthene or amixture of these or the crude' dehydrochlorination product can betreated to obtain piperityl esters, and on saponification thepiperitols. If either of the pure forms or a mixture of the two forms ofl-methoxy-Z-menthene is processed with the carboxylic acid, such asformic or acetic, and then the reaction product rich in esters issaponified, the product will generally consist of an easily separablemixture of hydrocarbons, formed by some dehydration of the piperitols,the piperitols and unchanged 1-methoxy-2-menthene(s). Similar processingof the crude dehydrochlorination mixture yields a somewhat more complexmixture, but satisfactory yields of piperitols are obtained. In general,treatment of the l-methoxy-Z-menthene-rich mixture, from thedehydrochlorination of the whole ether-chloride reaction product, with acarboxylic acid under optimum conditions for formation of piperitylesters will not alfect the impurities, including the carvotanacetylmethyl ether. This latter ether can be split with organic acids, but notas readily as can the desired ether, the l-methoxy-Z- menthene. Whilethe crude dehydrochlorination product can be used as a source ofpiperitols, the piperitols so produced are somewhat more difiicult toisolate pure, and I therefore prefer to utilize at least a partlypurified 1- methoxy-2-menthene for conversion to piperitols.

Although it is possible to isolate the individual alpha and beta formsof l-rnethoxy-2-chloro-p-menthane, I do not prefer to do so, but preferto avoid the cost of separating them, since each form dehydrochlorinatesto lmethoxy-Z-menthene, though at slightly different rates. Furthermore,while it is possible to separate the alpha and beta forms ofl-methoxy-Z-rnenthene, I prefer to avoid this expense, as eachindividual form yields a mixture of the two piperitols on splitting withan organic acid followed by saponification. It will be clear from theforegoing and from the examples that up to the piperitol stage, it isunnecessary to isolate individual cistrans forms of the itnermediateproducts whether optically active or racemic menthol is to be produced.Further, if racemic menthol is desired, an optically inactive startingmaterial for chloralkoxylation can be chosen and either the cis or transpiperitol or a mixture of these is suited for subsequent hydrogenationand isomerization to secure racemic methol.

On the other hand, if optically active menthol is to be produced, anoptically active starting material must be chosen for chloralkoxylation,and one of the piperitols produced will be convertible via itshydrogenation product to dextro rotatory menthol and the other to laevorotatory menthol, and therefore the two piperitols isolated are not ofthe same optical family. Therefore, the piperitols or theirhydrogenation products, neomenthol and isomenthol, should be separatedfrom each other prior to equilibration of the hydrogenated piperitols toproduce optically active menthol if this scheme of conversion is to beutilized. Similar considerations apply to the conversion products oflimonene, pinene, terpineol and other raw materials.

Having described the invention, what is claimed is:

1. The process which comprises treating a terpenic compound selectedfrom the class consisting of a-pinene and unsaturated compounds of thep-menthane series having as the sole cyclic double bond a carbon-carbondouble bond involving the cyclic carbon atom carrying the methyl groupand possessing a cyclic methylenic carbon atom alpha to the cyclicdouble bond and beta with respect to the cyclic carbon atom carrying themethyl group with molecular chlorine in the presence of a low molecularweight alcohol until not morethan about one mole of chlorine per mole ofmaterial being treated is reacted, treating the resulting chloroalkoxycompound with a strong base to remove the elements of HCl therefrom toform a tertiary allyl ether of the starting material.

2. The process of claim 1 in which the terpenic starting material iscarvomenthene and the alcohol is methyl alcohol.

3. The process which comprises treating a terpenic compound selectedfrom the class consisting of u-pinene and unsaturated compounds of thep-menthane series having as the sole cyclic double bond a carbon-carbondouble bond involving the cyclic carbon atom carrying the methyl groupand possessing a cyclic methylenic carbon atom alpha to the cyclicdouble bond and beta with respect to the cyclic carbon atom carrying themethyl group with molecular chlorine in the presence of a low molecularweight alcohol until not more than about one mole of chlorine per moleof material being treated is reacted, treating the resulting chloralkoxycompound with a strong base to remove the elements of HCl therefrom toform a tertiary allyl ether of the starting material, and reacting theresulting dehydrochlorinated material with carboxylic acid to form the3-acyloxy analogue of the starting material.

4. The process of claim 3 in which the terpenic starting 6.l-methoxy-Z-p-menthene.

7. The lower aliphatic alcohol ethers of Z-chloro-pmenthane-l-ol.

8. 1-methoxy-2-chloro-p-menthane.

9. The lower aliphatic alcohol ethers of 2,8-p-menthadiene-l-ol.

10. 1-methoxy-2,8-p-rnenthadiene.

11. The lower aliphatic alcohol ethers of 2-chloro-8- p-menthene-l-ol.

12.1-rnethoxy-2-chloro-S-p-menthene.

13. Compounds selected from the class consisting ofl-alkoxy-Z-p-menthene, 1-alkoxy-2,S-p-menthadiene,l-alkoxy-Z-p-menthene-S-ol, and 2-alkoxy-3-pinene, in which the alkoxyradical is the alkoxy radical of a lower aliphatic alcohol.

14. Compounds selected from the class consisting of1-alkoxy-2-chloro-8-p-menthene, l-alkoxy 2 chloro pmenthane-S-ol and2-alkoxy-3-chloro-pinane, in which the alkoXy radical is the alkoxyradical of a lower aliphatic alcohol.

References Cited in the file of this patent UNITED STATES PATENTS1,446,873 Brooks Feb. 27, 1923 2,360,898 Sarbach Oct. 24, 1944 2,361,532Cox Oct. 31, 1944 2,424,960 Bain et a1. Aug. 5, 1947 OTHER REFERENCESGalloway et al.: Chem. Abstracts, vol. 31, (1937), col. 672 (1 page).

Irwin et al.: Jour. Amer. Chem. Soc., vol. 63 (1941), pages 858-860.Simonsen: The Terpenes, 2nd ed., revised, vol. 1 pages 253, 269, 270,pub. by Cambridge Univ. Press (1953).

Summers: Chem. Rev., vol. (1955), page 336.

5. The lower aliphatic alcohol ethers of Z-p-menthene- ATENT OFFICEERECTION April 3 I962 UNITED STATES P CERTIFICATE 0]? C0 Patent No.3,028 418 Robert L. Webb certified that error appears in the that thesaid Letters Pa It is hereby above numbered patent requiring correctiona tent should read as eorrected belaw.

each occur- 26, 28 and 41, for "di- Column 3, lines 25 rence read Signedand sealed this 24th day of July 1962.

(SEAL) Attest: ERNEST w. sw 102a DAVID L. LADD Commissioner of PatentsAmazing Officer

3. THE PROCESS WHICH COMPRISES TREATING A TERPENIC COMPOUNDF SELECTEDFROM THE CLASS CONSISTING OF A-PINENE AND UNSATURATED COMPOUNDS OF THEP-MENTHANE SERIES HAVING AS THE SOLE CYCLIC DOUBLE BOND A CARBON-CARBONDOU BLE BOND INVOLVING THE CYCLIC CARBON ATOM CARRYING THE METHYL GROUPAND POSSESSING A CYCLIC METHYLENIC CARBON ATOM ALPHA TO THE CYCLICDOUBLE BOND AND BETA WITH RESPECT TO THE CYCLIC CARBON ATOM CARRYING THEMETHYL GROUP WITH MLECULAR CHLORINE IN THE PRESENCE OF A LOW MOLECULARWEIGHT ALCOHOL UNTIL NOT MORE THAN ABOUT ONE MOLE OF CHLORINE PER MOLEOF MATERIAL BEING TREATED IS REACTED, TREATING THE RESULTING CHLORALKOXYCOMPOUND WITH A STRONG BASE TO REMOVE THE ELEMENTS OF HCI THEREFROM TOFORM A TERTIARY ALLYL ETHER OF THE STARTING MATERIAL, AND REACTING THERESULTING DEHYDROCHLORINATED MATERIAL WITH CARBOXYLIC ACID TO FORM THE3-ACYLOXY ANALOGUE OF THE STARTING MATERIAL.